package com.imooc.contentcenter.config;

import com.alibaba.nacos.api.exception.NacosException;
import com.alibaba.nacos.api.naming.NamingService;
import com.alibaba.nacos.api.naming.pojo.Instance;
import com.alibaba.nacos.client.naming.core.Balancer;
import com.netflix.client.config.IClientConfig;
import com.netflix.loadbalancer.AbstractLoadBalancerRule;
import com.netflix.loadbalancer.BaseLoadBalancer;
import com.netflix.loadbalancer.Server;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.alibaba.nacos.NacosDiscoveryProperties;
import org.springframework.cloud.alibaba.nacos.ribbon.NacosServer;
import org.springframework.util.CollectionUtils;

import java.util.List;
import java.util.Objects;
import java.util.stream.Collectors;

/**
 * 同一集群优先调用和权重负载均衡
 * @Author lawhen
 * @Date 2020/12/29
 */
@Slf4j
public class NacosSameClusterWeightedRule extends AbstractLoadBalancerRule {

    @Autowired
    private NacosDiscoveryProperties nacosDiscoveryProperties;

    @Override
    public void initWithNiwsConfig(IClientConfig iClientConfig) {

    }

    @Override
    public Server choose(Object o) {

        try {
            //拿到配置文件中的集群名称 BJ
            String clusterName = nacosDiscoveryProperties.getClusterName();
            BaseLoadBalancer loadBalancer = (BaseLoadBalancer) this.getLoadBalancer();
            //想要请求的微服务的名称
            String name = loadBalancer.getName();
            //拿到服务发现的相关API
            NamingService namingService = nacosDiscoveryProperties.namingServiceInstance();
            //1.找到指定服务的所有实例 A
            List<Instance> instances = namingService.selectInstances(name, true);
            //2.过滤相同集群下的所有实例 B
            List<Instance> sameClusterInstances = instances.stream().filter(
                    instance -> Objects.equals(instance.getClusterName(), clusterName)).collect(Collectors.toList());
            //3.如果B是空，就用A
            List<Instance> instancesToBeChosen;
            if (CollectionUtils.isEmpty(sameClusterInstances)) {
                log.warn("发生跨集群调用，name={},clusterName={},instances={}", name, clusterName, instances);
                instancesToBeChosen = instances;
            } else {
                instancesToBeChosen = sameClusterInstances;
            }
            //4、基于权重的负载均衡算法，返回一个实例
            Instance instance = ExtendBalancer.getHostByRandomWeight2(instancesToBeChosen);
            log.info("选择的实例是:port={},instance={}", instance.getPort(), instance.getIp());
            return new NacosServer(instance);
        } catch (NacosException e) {
            e.printStackTrace();
        }
        return null;
    }
}

//封装权重选择算法
class ExtendBalancer extends Balancer {
    public static Instance getHostByRandomWeight2(List<Instance> hosts) {
        return getHostByRandomWeight(hosts);
    }
}